Update ci-testing.yml streamlined tests

[glenn-jocher]

Update tests per Colab CI updates in yesterday's PR.

🛠️ PR Summary

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🌟 Summary

Improved YOLOv5 CI testing workflow refinement for better maintainability and readability. 🛠

📊 Key Changes

• Simplified and refactored the testing script to use loop structures, improving code clarity. 🔄
• Renamed variables for better understanding (d to m, best to b). 🔤
• Unified image size and batch commands under one variable (imgsz). 🖼
• Reduced code duplication by using loops for device and weight iterations. ♻️

🎯 Purpose & Impact

• This refactoring makes the CI testing workflow easier to read and maintain. ✨
• By using loops, future changes to the script can be made in fewer places, reducing potential errors. 🛠
• Cleaned-up variable names make it easier for new contributors to understand the code. 📝
• These improvements will indirectly enhance the reliability of the YOLOv5 testing process. 🔍